Prior treatment of an enlarged and/or tumorous prostate has involved transurethral or transrectal resection of the prostate tissue with the attendant problems associated with such procedures.
In recent years, cryosurgical techniques have been applied to tumorous tissues with considerable success. These techniques succeed in reducing the tissue while avoiding the attendant complications of more conventional surgical techniques. The principal difficulty in applying cryosurgery to internal organs is accurate placement of cryosurgical probes. Generally, imaging techniques are used to provide a visual representation of the desired organ and the surgeon observes the image while he guides probes into place. A popular imaging technique is ultrasound wherein a transducer is placed against the body and transabdominal scans are made to image the internal organs. The image resolution of such scans is limited due to the intervening abdominal tissues, so ultrasound probes which can be inserted into natural body orifices or through cannulas so as to be closer to the target organs are used for deep tissue imaging.
In the case of cryosurgery of the prostate, accurate placement of the cryoprobes is important to control the areal extent of freezing and to avoid damage to surrounding tissues such as the urethra and the rectal wall. This in turn requires high resolution imaging and a way to achieve accurate placement of the cryoprobes relative to the ultrasound probe used to produce the image. Imaging of the prostate is readily obtained by use of an ultrasound probe inserted into the patient's rectum. Because of the proximity of the prostate to the rectum, a high resolution image is obtained and the ultrasound probe can be used as basis from which to gauge probe placement. What is therefor needed is an insertion guide which is securely mountable on the ultrasound probe to provide an adjustable but stable guide which can be used to accurately position biopsy needles within the prostate relative to the ultrasound probe.
Biopsy needle guides which attach to ultrasound probes and transducers for use in positioning needles in tissues being imaged are known as represented by U.S. Pat. No. 4,742,829, Law, et al. U.S. Pat. No. 4,838,506, Cooper, U.S. Pat. No. 4,898,178, Wedel and U.S. Pat. No. 5,052,396. Wedel, et al. However, none of these prior guides provide the combination of adjustability and stability which is necessary to accurately position biopsy needles and, ultimately, cryoprobes in a prostate relative to a rectally inserted ultrasound probe. For example, the device of U.S. Pat. No. 4,742,829 is fixed to a vaginally inserted probe in such a manner that the needle guided thereby is immediately adjacent to the probe so as to extend therealong into tissues located proximally of the probe. No adjustment perpendicular to the probe is available. U.S. Pat. Nos. 4,898,178 and 5,052,396 disclose a needle guide for use with an externally positioned transducer wherein the needle is inserted at a continuously fixed angle relative to the transducer. Adjustment of the position of the needle is limited to its rotary position about the transducer. The device of U.S. Pat. No. 4,838,506 is applicable to an insertable transducer and provides a guide which is adjustable in two dimensions. However, it is of extremely simple construction and does not provide the degree of stability necessary for accurate insertion of biopsy needles and cryoprobes through a patient's perineum and into the prostate.